The structure of the keratan sulphate chains attached to fibromodulin isolated from articular cartilage.

This research article examines the structure of keratan sulphate chains attached to a protein called fibromodulin sourced from animal cartilage. The investigators discovered key differences in the structure when comparing chains found in articular cartilage to those found in tracheal cartilage.

Methodology and findings

The scientists performed a detailed investigation of the structure of keratan sulphate chains that are attached to fibromodulin, a protein isolated from bovine and equine articular cartilage.

• Firstly, keratanase II was used to break down the keratan sulphate chains into smaller components, or oligosaccharides.
• These oligosaccharides were then isolated and their structures determined through high-field 1H-NMR spectroscopy and high-pH anion-exchange chromatography. NMR spectroscopy is a technique used to identify the physical and chemical properties of atoms or molecules, while chromatography is a method used to separate and analyze complex mixtures.
• They found both alpha(2-6)- and alpha(2-3)-linked N-acetylneuraminic acid in the capping oligosaccharides, along with fucose, which is alpha(1-3)-linked to N-acetylglucosamine as a branch in both the repeat region and capping oligosaccharides.

Results and significance

Through their analysis, the researchers discovered some important structural variations:

• They noticed a significant difference in the structures of N-linked keratan sulphate chains attached to fibromodulin depending on their origin. The chains derived from articular cartilage significantly differed from those derived from tracheal cartilage.
• Fibromodulin from tracheal cartilage lacked both alpha(2-6)-linked N-acetylneuraminic acid and alpha(1-3)-linked fucose which were found in the ones from articular cartilage.
• They established that the keratan sulphate chains were short in length, consisting of only eight or nine disaccharides.
• The study also determined significant variations in the levels of galactose sulphation at the non-reducing end of the chain, which could suggest potential functional importance.

These important structural differences may have implications in terms of function which could contribute to our understanding of how fibromodulin and keratan sulphate chains operate within the body. Such findings might also provide insight into the development of diseases related to cartilage and joints.